Five Auckland residents hospitalised with carbon monoxide poisoning last night were believed to be running a generator in the garage because they couldn't get their power connected.

An ambulance was called at 12.22am after a family friend found the people "on the ground" at the Jever Pl house, in the suburb of Massey.

The group, two males and three females, between nine and 53 years old, had been subjected to heavy doses of carbon monoxide, believed to have come from a malfunctioning petrol generator.

A Cartmel Ave resident, whose property backs on to the house in question, said she was stunned when a man knocked on the door on Friday asking to run a plug between the houses because their power could not be connected until today.

"We were shocked by what he wanted to do and said it was illegal and very dangerous," she said.

A Fire Service spokeswoman said: "We arrived to find five people on the ground in the house all semi-conscious from carbon monoxide poisoning."

Police said a family friend had been called to the house by one of the occupants when they began feeling unwell.

"He arrived and found the occupants in a severe state of distress and notified emergency services," a police spokesman said.

The group were all taken to North Shore Hospital.

The house, which had a digger out front and looked to be under development, was cordoned off this morning. Police were to begin a scene examination assisted by the Fire Service "to determine the cause of the high levels of carbon monoxide".

The police spokesman said initial reports were that a petrol generator was being used in an attached garage to supply power to the house.

Doors and windows were open at the home this morning.

Neighbours leaving for work did not know the people living at the house but said they had recently moved in.